Multi-speed accessory drive

ABSTRACT

A multi-speed accessory drive employing a planetary gear reduction set. A cone clutch linked to an output member, a ball ramp actuator for moving the cone clutch into engagement with the output member and a brake for selectively controlling the rotation of the ring gear of the planetary gear set.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention is related to clutching devices generally and morespecifically to an engine driven apparatus for driving at least onevehicle mounted accessory at either one of two selectable speeds as wellas being able to totally disengage (zero speed) the accesory.

Planetary gear sets are often used in drive units for speed changingapplications by selectively restraining one of either the ring gear, thesun gear or the planet gear carrier. One such drive unit is illustratedin U.S. Pat. No. 2,959,070. In the context of an accessory drive unitfor automotive applications the planet gear set may be employed as ameans for driving the accessory at a speed that is different from thespeed of the engine (crankshaft). Overdriving the accessory, that is, todrive it faster than the speed of the engine reduces the useful life ofthe gear unit and often generates an unacceptable level of accousticwhine. Further, prior drive units have used planetary gear sets to drivethe accessory at only either of two speeds. The first speed being equalto input speed and the second speed differing from the first by theeffective gear ratio of the gear set. It is desirable and often anecessity with smaller displacement engines to be able to disengage theaccessories when starting the vehicle. This feature is especiallyimportant during cold start to lessen the drag on the engine.

It is an object of the present invention to provide an engine driven,clutched drive capable of driving a belt driven accessory to full speed,reduced speed and zero speed (disengaged). A further object is toprovide such a device utilizing a speed reducing planetary gear set. Anadditional object of the present invention is to provide means forperforming the clutching function in a simple manner. Many other objectsand purposes of the invention will become apparent from the detaileddescription.

Accordingly the invention is directed to:

A multi-speed accessory drive having a plurality of operating conditionsin which an output member is rotated at the speed of an input or drivingmember, at a reduced speed ratio or at zero speed comprising: a pressureplate axially movable relative to the input member, and a driving linkrotatably fixed to the input member and to the pressure plate forrotating the pressure plate and for axially urging the pressure plateaway from the driving link. The drive further includes means for movingthe pressure plate into contact with and for rotational engagement withthe output member and for alternatively drivingly connecting the outputmember to the input member; and means for disengaging the ring gear ofthe planetary gear set during intervals when the pressure plate is inengagement with the output member to permit the output member to rotateat the speed of the input member, for halting the rotation of the ringgear when the pressure plate is disengaged from the output member topermit the output member to rotate at a predetermined ratio of the speedof the input member and for disengaging the ring gear during intervalswhen the pressure plate is disengaged from the output member therebypermitting said output member to remain stationary while the inputrotates.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partial cross-sectional view of a multi-speed accessorydrive constructed in accordance with the present invention.

FIG. 2 is a cross-sectional view of the drive illustrated in FIG. 1.

FIG. 3a is a front view of an alternate embodiment of the drive linkshown in FIG. 1.

FIG. 3b is a side plane view of the alternate drive link of FIG. 3a.

FIG. 4 is a projected view of the embodiment of the invention shown inFIG. 1.

FIG. 5 and 6 illustrate an alternate braking mechanism.

FIG. 7 illustrates an actuation arm shown in FIGS. 5 and 6.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompaning FIGURES which illustrate amulti-speed accessory drive 10 which incorporates an off-mode ofoperation. With reference to FIG. 1, the drive 10 incorporates a speedreducing planetary gear set generally indicated as 12 comprising a sungear 14, a plurality of planet gears 16 positioned in surroundingrelation relative to the sun gear and a ring gear 18 positioned indriving relation about the plurality of planet gears. FIG. 1 illustratesbut one of the planet gears 16, such construction being known to onefamilar with the art.

The sun gear 14 is mounted to and rotates with an input member or shaft20 which is illustrated in FIGURE 1, supports a number of othercomponents of the drive 10. The shaft 20 is connected to a rotatingmember of the engine, such as its crankshaft (not shown) by means of abolt 22 and a washer 24. The planet gears 16 are connected to a planetcarrier 40 which is connected to an axially extending hub 80 concentricto the input member 20. The ring gear 18 is positioned by housingmembers 44 and 46 which are isolated from the input member 20 and anaxially extending hub 80 by bearings 50 and 52. The housing members 44and 46 define a lubrication cavity 83 for oil or the like. In theembodiment of the invention shown in FIG. 1 a disk 54 is attached to androtatable with the ring gear 18. The rotation of the ring gear 18 anddisk 54 is controlled by a braking device such as the brake caliper 56shown in FIG. 4. The caliper 56 may be pneumatically or hydraulicallyactivated in a known manner in response to control signals. FIGS. 5 and6 illustrate an alternate means 319 for stopping the rotation of thering gear 18.

Returning to FIG. 1 it can be seen that the planet carrier 40 extendsradially downward from the planet gears and is attached to the hub 80which is rotationally supported relative to the input member 20 by abearing 82, such as the double race bearing. The hub 80 supports anoutput pulley 84 which may be attached thereto by screws 85 or similarmeans. The pulley 84 comprises a radially extending portion or member 86which terminates at a pulley face 88.

The drive 10 further includes a cone clutch 89 which includes a pressureplate 90. The pressure plate 90 includes a radially extending portion 92and a conically shaped ring 98 coaxially positioned to the shaft 20. Thering 98 includes a tapered surface 100 which acts as a conicalengagement surface as hereinafter described. The base 96 of the pressureplate 90 is supported and rotationally isolated from the shaft 20 by aspacer 102 and a bushing 104. In this manner the pressure plate 90 isfree to move axially on the bushing 104.

The cone clutch 89 further includes a cover 110 comprising a taperedinner surface 112 which supports a ring of a friction material 114,which acts a conical friction surface for engagement with the taperedsurface 100. The cover 110 extends from and rotates with the pulley 84.

A drive link 120 is positioned between the pulley 84 and pressure plate90. The drive link 120 is attached to and rotates with the shaft 20. Akey 122 may be used to connect the drive link 120 to the shaft 20. Thedrive link 120 includes a radially extending portion 124 which supportsa plurality of springs 126a-f, shown in greater detail in FIG. 2. Thesprings 126 in the embodiment of the invention shown in FIGS. 1 and 2comprise a plurality of leaf springs which are attached at one endgenerally shown as 128 by rivots 130 or the like to the radial portion124 of the drive link 120 and attached at their other end 132 to theradially extending portion 92 of the pressure plate 90.

An alternate embodiment of the drive link 120 is shown in FIG. 3a andgenerally designated as 300. This alternate embodiment combines thestructural features of the drive link 120 and the springs 126 into aunitary structure. More specifically the drive link 300 comprises acentral hub 302 defining an opening 304 which is sized to receive theshaft 20. A side view of the drive link 300 is shown in FIG. 36. The hub302 further includes a keyway 306 for receiving a key such as key 122 aspreviously described. Radially sweeping outward from the hub 302 are aplurality of flexible spring-like arms 310a-e which also extend axiallyoutward from the hub 302 and terminate at ends 312. The ends 312 aresubstantially flat and are adapted to be attached to the radial portion92 of the clutch plate 90 in the manner that the springs 126 wereattached.

The pressure plate 90 is clutched or moved into contact with thefriction material 114 by the operation of an actuator 200 shown inFIG. 1. One such actuator is a ball ramp actuator which includes aplurality of balls 202 supported by a pluralityof ball ramps 204 and 206in a known manner. The ramps 204 and 206 are each supported by theirrespective ramp support members 210 and 212. These ramp support membersare rotationally isolated from the input member 20 by means of thethrust bearings 220 and 222. More specifically, bearing 220 supports theramp support member 210 relative to the base 96 of the pressure plate 90while bearing 222 supports the other ramp support member 212 relative tothe spacer 102 secured relative to the input member 20 by a key 122.

To activate the ball ramps 204 and 206 their respective ramp supports210 and 212 are rotated relative to one another. This is accomplished bysecuring the circular flange 230 of the support 212 to a bracket 232which is attached to the engine block as shown in FIG. 4. The circularflange 236 of the support 210 is moved by a rack and pinion mechanism,generally designated as 240. This mechanism 240 comprises a rack 242secured to the flange 236, and a pinion gear 244 d riven by a motor 246.The motor 246 is responsive to control signals generated by anelectronic control unit (ECU) (not shown) and secured by a bracket 248to the engine. In this manner the ramp support 210 can be rotated eitherclockwise or counter clockwise relative to the ramp support 212 thuscausing the clutch plate 90 to move axially inward and outward relativeto the friction material 114.

Reference is again made to FIG. 1 which, illustrates the clutch plate 90in an engaged or clutched mode of operation with tapered surface 100 ofthe clutch plate 90 engaging the friction material 114. If it is desiredto totally disengage the accessory (not shown) driven by the pulley 84,the braking mechanism such as the caliper 56 is deactivated thuspermitting the disk 54 to rotate freely and the rack and pinionmechanism 244 is rotated in a manner to cause the ramp support 210 tomove to the right as viewed in FIG. 1. The pressure plate 90 will movewith the ramp support 210 thereby disengaging it from the frictionmaterial 114. In this operating mode the pulley 84 will free wheel aboutthe input shaft. A low speed mode of operation is achieved bymaintaining the clutch plate 90 disengaged from friction material 114 asdescribed above and by actuating the brake 56 to prevent the disk 54from rotating. In this operating condition the output pulley 84 isdriven through the speed reducing planetary gear set 12 and moreparticularly, the output pulley 84 is driven through the sun gear 14,the planet gears 16, the planet carrier 40 and hub 80. In thisdeclutched mode of operation, the ring gear 18 will have a tendency torotate in a direction opposite the direction of rotation of the inputshaft. The ring gear rotation is conveniently halted by application ofthe caliper 56. Having restrained the ring gear 18 from undesiredrotation, the output pulley 84 will thereafter rotate at a reduced ratiorelative to the speed of the input member 20. When it is desired toincrease the speed of the output pulley 84, that is, to drive the pulley84 at shaft speed, the ramp support 210 is rotated by the rack andpinion mechanism 240 which creates a corresponding relative separatingmotion between the ramps 204 and 206 causing the ramp 204, the rampsupport 212 and thrust bearing 220 to move axially inward toward thepulley 84. This movement of the thrust bearing 220 causes the clutchplate 90 to move into contact with the friction material 114 connectedto the output pulley 84. In this operting condition, the output pulley84 is driven at the speed of the shaft 22 through the key 122, driveline 120, springs 126, pressure plate 90 and friction material 114. Inas much as it is undesirable to restrain the ring gear 18 as describedfor low speed operation the caliper 56 is deactivated.

Reference is now made to FIG. 5 and 6 which illustrate an alternatemeans 319 of controlling the rotation of the ring gear 18. Thisalternate embodiment replaces the disk 54 and braking device 56previously discussed. With reference to FIG. 6 there is illustrated anend view of the drive 10. As mentioned, the disk 54, which is not neededfor this alternate embodiment has been eliminated. Positionedcircumferentially about the ring gear 18 is a flexible band 320 havingends 322 and 324 terminating at a short tube or ferrule 323 and 325respectively. The band 320 supports on an interior side thereof a lengthof friction material 326. The band 320 and friction material 326partially circumscribe the ring gear 18. In the preferred embodiment ofthe invention the friction material 326 wraps about the ring gear 18 forapproximately 240 degrees (wrap angle). The alternate braking devicefurther includes a pivotably supported actuation arm generallydesignated at 330. The arm 330 comprises a lever supported at a fulcrumpoint generally designated as 332 and includes lever arms 334 and 336.Extending from the arms 334 and 336 are rods 333 and 335 respectivelywhich are loosely received within one of the tubes or ferrules 323 and325. The rods 333 and 335 are more clearly shown in FIG. 7. It ispreferable that lever arm 334 be greater than lever arm 336. In theillustrate embodiment of the invention the ratio of arms 334 to 336 isapproximately 2.25. This ratio, as well as the wrap angle of 240 degreesminimizes band tension while permitting placement of these components inthe small working space available. The arm 330 includes an extension 338which is attached to a non-moving part of the engine. The means ofattachment of the extension 338 to the engine can be by utilizing aspring 340 or a movable solenoid 342 as illustrated in FIG. 6.

Assuming that extension 338 is attached tot he spring 340, the spring340 will lightly bias the band 320 into engagement with the ring gear 18as shown in FIG. 5. The rotation of the ring gear 18 in the direction asshown by the arrow causes the band 320 to self-tighten thus providing abraking force to stop the rotation of the ring gear 18. To achieve thelow speed mode of operation the actuator 200 is disengaged, that is, thepressure plate 90 is moved out of engagement with the friction material114. As previously mentioned, in this condition the ring gear 18 willtend to rotate opposite to the shaft 20 in the direction shown in FIG.5. Due to the self-tightening or self-actuating feature of the alternatebraking mechanism 319 this undesired reverse rotation of the ring gear18 is automatically stopped.

During high speed operation the actuator 200 is engaged and as describedabove, the ring gear 18 will tend to rotate with the shaft 20 in asubstantially clockwise direction as viewed in FIG. 5. However, due tothe unequal lengths of the lever arms 334 and 336 such rotation of thering gear 18 will tend to loosen the band 320 situated about the ringgear 18 thus permitting the ring gear to rotate relatively free of thedrag forces created by the friction material 326.

A further embodiment of the invention is shown in FIG. 6. Thereplacement of the spring 340 with a solenoid device 342 having amovable armature 344 permits the end 325 of the band 320 to moveinwardly toward the ring gear 18, upon extention of the armature 344thus moving the band 320 away from the ring gear for totaldisengagement. The operation of the solenoid device 242 is controlled inconcert with the operation of the actuator 200, that is, during the lowspeed mode of operation, with the actuator 200 disengaged the armature344 is moved to tighten the band 320 about the ring gear 18 therebypreventing its rotation. During high speed operation with the actuator200 is disengaged and the armature is moved to cause the band 320 tomove out of engagement with the ring gear 18 permitting it to rotate inthe direction of the shaft 20. A cover (not shown) may be utilized toenclose the band 320 and ring gear 18 to protect these structuralcomponents from contamination. Retraction of the armature 344 causes theband 320 to move into engagement with the ring gear thus stopping itsrotation during low speed operation.

Many changes and modifications in the above-described embodiment of theinvention can, of course, be carried out without departing from thescope thereof. Accordingly that scope is intended to be limited only bythe scope of the appended claims.

What is claimed is:
 1. A multi-speed accessory drive having a pluralityof operating conditions in which an output member is rotated at thespeed of an input member, at a reduced speed ratio or at zero speedrelative thereto; the drive comprising:a planetary gear set comprising asun gear, a plurality of planet gears and a ring gear interconnectedwith said sun gear, wherein said sun gear is drivingly connected to theinput member and said planet gears are drivingly connected to the outputmember a pressure plate axially movable relative to the input member, adriving link rotatably fixed to said input member including spring meansfixed to said input member and to said pressure plate for rotating saidpressure plate and for axially urging said pressure plate away from saiddriving link; means, including a ball ramp actuator, for moving saidpressure plate into contact with and for rotationally engaging saidoutput member and for alternatively drivingly connecting said outputmember to said input member; and means for disengaging said ring gearduring intervals when said pressure plate is in engagement with saidoutput member to permit said output member to with said output member topermit said output member to rotate at the speed of the input member,for halting the rotation of said ring gear when said pressure plate isdisengaged from said output member to permit said output member torotate at a predetermined ratio of the speed of said input member andfor disengaging said ring gear during intervals when said pressure plateis disengaged from said output member to achieve said zero speed therebypermitting said output member to remain stationary while said inputmember rotates wherein said disengagement means comprises a discrotationally fixed to said ring gear and isolated from said input memberand means comprising a brake caliper for selectively inhibiting therotation of said disc and wherein said ball ramp actuator comprises aplurality of ramp supports rotationally isolated from the rotation ofthe input member and from said pressure plate and rotationally movableone relative to one another, said ramp supports supporting means formoving said pressure plate axially in response to the relative rotationof said supports including means for rotating said supports relative toone another comprising a rack and pinion mechanism connected to one ofsaid ball ramp supports and including a motor responsive to controlsignals input thereto for moving said one ball ramp support and whereinthe other of said ball ramp supports includes means for preventing samefrom rotating.
 2. The drive is defined in claim 1 wherein said pressureplate is slidably supported relative to said input member by a bushing.3. A multi-speed accessory drive having a plurality of operatingconditions in which an output member is rotated at the speed of an inputmember, at a reduced speed ratio or at zero speed relative thereto; thedrive comprising:a planetary gear set comprising a sun gear, a pluralityof planet gears and a ring gear interconnected with said sun gear,wherein said sun gear is drivingly connected to the input member andsaid planet gears are drivingly connected to the output member, apressure plate axially movable relative to the input member, a drivinglink including spring means rotatably fixed to said input member forrotating said pressure plate and for axially urging said pressure plateaway from said output member, means, including a ball ramp, for movingsaid pressure plate into contact with and for rotationally engaging saidoutput member and for alternatively drivingly connecting said outputmember to said input member; and means for disengaging said ring gearduring intervals when said pressure plate is in engagement with saidoutput member to permit said output member to rotate at the speed of theinput member, for halting the rotation of said ring gear when saidpressure plate is disengaged from said output member to permit saidoutput member to rotate at a predetermined ratio of the speed of saidinput member and for disengaging said ring gear during intervals whensaid pressure plate is disengaged from said output member to achievesaid zero speed thereby permitting said output member to remainstationary while said input member rotates wherein said ball rampactuator comprises a plurality of ramp supports rotationally isolatedfrom the rotation of the input member and from said pressure plate androtationally movable one relative to one another, said ramp supportssupportng means for moving said pressure plate axially in response tothe relative rotation of said supports including means for rotating saidsupports relative to one another comprising a rack and pinion mechanismconnected to one of said ball ramp supports and including a motorresponsive to control signals input thereto for moving said one ballramp support and wherein the other of said ball ramp supports includesmeans for preventing same from rotating.
 4. The drive as defined inclaim 3 wherein said disengagement means comprises a disc rotationallyfixed to said ring gear and isolated from said input member and meansfor selectively inhibiting the rotation of said disc.
 5. The drive asdefined in claim 4 wherein said inhibiting means comprises brakecaliper.